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Forecast discussion:
Note: I'm nearing the end of my two week family camping trip. My available bandwidth is very low so I'm keeping posts shorter than normal and less graphically intensive.
We are clearly in the where's-the-monsoon-moisture? time of year. The giant upper air ridge and high center (Figure 1) are parked almost on top of Longmont Tuesday. It won't move far by Wednesday, explaining the 100°F + temperatures. Remember, we average one 100°F + day every other year... so we've really hit the heat hard this year so far. I've indicated the tropical moisture flow as dark green arrows. The circulation around the high is pushing it all to the south and up into the west and over us to the north.
This high is also stirring the smoke from various Western U.S. fires making the skies mildly milky. This probably won't clear out in the near future.
You can see the above mentioned moisture as the grey and white colors in Figure 2 - the water vapor satellite image. The change that is coming over these two days comes from the high migrating eastward and the moisture plume bending eastward with it to give Colorado cooler temperatures and chances of thunderstorm rainfall. Thursday and Friday will see a chance of storms statewide, but no severe weather is predicted at this time.
The longer range forecast:
After cracking 100°F early week, we cool to around 90°F (just a bit above average) and thunderstorm chances return. Saturday looks dry and hot again (as the plume moves east of us briefly) then the moisture rocks back to cover Colorado early next week.